Urinary Incontinence is a significant, and growing, concern for women with a prevalence of 53.2%. The total cost of treating urinary incontinence in 1995 was $26.3 billion. Urinary incontinence (UI) affects more then 35 million Americans, most of whom are women. Approximately 12 million women sought physician treatment for UI in 2004. That number is expected to grow to 16.3 million in 2010.
Factors contributing to UI in women include anatomic (a shorter urethral length and a disruption of the urethral support as a result of vaginal delivery), genetic, obesity, diabetes, etc. All of these factors are increasing with the shift of population demographics. Stress Urinary Incontinence (“SUI”) is the predominant form of UI and is primarily caused by a weakened pelvic floor which leads to hypermobility, or the movement of the urethra under exertion. SUI is the most common type of urinary incontinence in women. Risk factors for stress incontinence include female sex, advancing age, childbirth, smoking, and obesity. Conditions that cause chronic coughing, such as chronic bronchitis and asthma, may also increase the risk and/or severity of symptoms of stress incontinence.
SUI is a bladder storage problem in which the urodynamics of the urinary tract are altered (typically through childbirth), and the sphincter is not able to prevent urine flow when there is increased pressure from the abdomen. Stress incontinence may occur as a result of weakened pelvic muscles that support the bladder and urethra, or because of malfunction of the urethral sphincter. Both of these lead to a reduction in the pressure required to pass urine through the urethra. Thus, increases in pressure from everyday activities can cause the emission of a small amount of urine. Approximately 50% of women in the US have occasional urinary incontinence and approximately 14 million of them present with symptoms of SUI which require intervention. Most women accept the inconvenience of incontinence, utilizing pads and protective underwear as a silent treatment option.
The realignment of the urethra during acts such as lifting, laughing, coughing, or many daily activities can change the hydrodynamics of the bladder-urethral plumbing, resulting in unintended urinary leakage. Pharmaceuticals are the primary physician-directed treatment, representing $1.2 billion in annual expenditures. Pharmaceuticals and pads do not provide permanent relief, but impose a constant economic drain with undesirable physical side-effects. An additional factor of significance is the effect on depression in sufferers. It has been determined that after adjusting for morbidity, functional status, and demographic variables, women with severe and mild-moderate incontinence were 80% and 40%, respectively, more likely to have depression than continent women.
Hypermobility may be treated surgically by the insertion of a tape between the vaginal wall and the urethra to act as a sling for the urethra to diminish unintended urinary leakage. There were 175,000 sling procedures performed in the US in 2004. The use of bulking agents to decrease urethral diameter and compliance has also shown some success, with 60,000 bulking procedures performed in the US in 2004. In attempts to replace invasive surgery and implants with minimally invasive approaches, work has been performed by Dmochwski, Ross, and Fulmer to show some clinical utility to thermally remodeling the collagenous structure of the pelvic floor to reduce hypermobility.
In the 1990s the standard procedure was to apply a “sling” by wrapping a sheet of material around the urethra (inserted through a vaginal incision, placed between the urethra and vagina, and attach at both ends to the pubis). The “sling” or “hammock” formed thusly would replicate a healthy endopelvic fascia. That is, it would pull the urethra in a superior/posterior direction, restoring normal anatomy and increasing the hydrostatic pressure required to void the bladder. Additionally, and just as important, the sling is less prone to deformation under pressure than the damaged endopelvic fascia. This treatment is still performed today and is prevalent in cases where the integrity of the endopelvic fascia is so degraded that the bladder prolapses into the vagina.
One of the primary treatments employed today is endoscopic placement of a narrow tape (1 cm wide by 40 cm long) through a single incision in the midline of the vagina, just below the urethra. The tape is pulled taught through two suprapubic incisions and held in place by tissue formation during the healing process. The tape material is less elastic than the damaged endopelvic fascia and more resistant to distension during periods of exertion.
There are published improvement rates of greater than 90% and cure rates greater than 80%. The interventions are surgical, however, and require significant anesthetic intervention as well as incisions in the vagina and (in the case of transvaginal tape) in the suprapubic region. Failure rates are reported in the 5% to 10% range and consist primarily of bladder perforation, immediate post-procedure retention, infection, and novo incontinence at some period post procedure.
A minimally invasive approach using radiofrequency (RF) electrical current to heat and remodel the endopelvic fascia has been attempted in recent years. Radiofrequency Bladder Neck Suspension (RFNS) requires exposing the endopelvic fascia via two 2 cm incisions through the mucosal and submucosal membranes of the superior/lateral aspects of the vagina. A bipolar radiofrequency probe is applied to the exposed endopelvic fascia, inducing resistive heating as the alternating current passes through the tissue. RF thermal remodeling of the endopelvic fascia causes the collagenous structure to remodel and shrink. The treatment does affect a positive benefit, with longer-term cure rates at greater than 75%. The underlying science of this approach is sound as thermal energy shrinks the collagen by affecting the basic structure of the molecule. Collagen is typically a triple helical chain of proteins, with cross-linking along the chain to maintain the structure. Wall and others have confirmed that thermal remodeling of collagen does occur in different time intervals in relation to elevated temperatures.
Minimally invasive attempts at radiofrequency (RF) remodeling of the endopelvic fascia have been inconsistent because the physics of RF ablation (including tissue resistivity variability) do not allow the consistent of predictable application of therapeutic levels of energy at levels as deep as 10 mm and without causing injury to the vagina.